1. Field of the Invention
The present invention relates to a coupling for connecting a container to means for sucking fluid filled in the container, while breaking thin sealing film attached to the opening of the container.
2. Description of the Related Art
There have been well-known automatic vending machines of the bag-in-box type (which will be hereinafter referred to as BIB type) wherein plastic-made flexible containers filled with drinks such as coffee and juice and transported in boxes made by corrugated cardboard are set in the automatic vending machines.
According to the automatic vending machines of the BIB type, it is not needed to collect those containers which have become vacant after fluid drinks therein are drunk up. This is quite excellent in that the running cost of the automatic vending machines can be reduced and also sanitary in that fluid in the container can be sucked by a pump without exposing the fluid to the air.
Japanese Patent Disclosure Sho 62-258288 discloses a coupling for connecting a container housed in the automatic vending machine to means for sucking fluid filled in it.
The coupling disclosed in this reference comprises a female connector attached to the container and a male connector fitted into the female connector. When the male connector is fitted into the female one, thin film bonded to the female connector is broken with a tip portion at the front end of the male connector and the container is thus opened. When the male connector is further pushed into the female one under this state, a valve in an inner cylinder of the male connector is opened to communicate the container with a fluid passage in the male connector. When the male connector is pulled out of the female one, the valve in the male connector is closed to shield the inside of the piping in the male connector from outside air and prevent fluid left in the piping from coming out of it.
Japanese Utility Model Disclosure Hei 3-69392 also discloses a coupling wherein a valve in the coupling is opened and closed associating with the operation of a suction pump connected to the coupling to shield fluid in the container from the air so as to increase the sealing capacity of the container.
In the case of the couplings disclosed in the above-mentioned references, however, the connecting of these couplings could not be made smooth because of the connecting resistance of the male connector (or plug) relative to the female connector (or socket) and the sliding resistance of seal rings used, and because the pressing force of the male connector applied to the thin film to break it was larger than expected.
The inventor of the present invention repeated tests of breaking aluminium foil with the conventional socket which included a cutter section in the socket comprising a tip potion shaped like a cone and a trunk portion continuous from the tip portion shaped like a cylindrical pole. As the result, it has been found that the aluminium foil is broken not from its area on which the tip potion of the cutter section abuts but substantially from its center in three directions, that load applied to push and spread the aluminium foil with the cylindrical trunk portion of the cutter section is larger than load needed to break the aluminium foil by the tip portion of the cutter section at the initial stage, and that the aluminium foil is liable to be peeled off from the opening of the female connector and its pieces thus peeled off are mixed into the fluid in the container because it is pushed and spread at its area adjacent to the opening rim of the female connector by the cylindrical trunk portion of the cutter section.